This invention relates to a process and an apparatus for detection of a cardiac movement or cycle of a patient. More particularly, the invention relates to the detection of the cardiac cycle starting from an angiogram of coronary vessels. Identification of cardiac movement from images of coronary arteries acquired using a radiography apparatus during selective injection of a contrast agent within these coronary arteries, can be useful in a number of algorithms:
Calculation of a myocardial perfusion index based on analysis of the variation of density in a series of images throughout different cardiac cycles.
Production of a fixed sequence, in other words a sequence with no or very few displacements of the coronary arteries between the different images making up the sequence.
Synchronization of two multi-modal sequences for the same patient, for example, one sequence acquired in fluoroscopy and another sequence acquired in conventional recording mode, the images of the two sequences possibly being combined.
Production of a three-dimensional image reconstruction by applying known reconstruction algorithms from a series of images chosen to illustrate the same instant in the cardiac cycle.
There are difficulties with these algorithms. A first difficulty is that the electrocardiogram (ECG) signal is necessary to know the instant in the cardiac cycle associated with each image acquired in the sequences. But this signal is not always directly available with the images. Furthermore, the ECG signal is an electrical signal that describes the stimulation of the heart muscle but not the effective mechanical movement of this muscle. However in the known application of algorithms, it is necessary to know the position of injected coronary arteries, in other words to know the mechanical behaviour of the heart
A second difficulty is that the patient might breath during the acquisition or that the images from two different cardiac cycles may be slightly different.